Insights into brachyuran crab phylogeny: exploring the mitochondrial genome of Arcotheres sinensis (Brachyura, Pinnotheridae).

The phylogeny of species of Brachyura, particularly within the family Pinnotheridae, remains incompletely understood. To enhance the taxonomy and systematics of the Pinnotheridae, we conducted a comprehensive study aimed at elucidating the phylogenetic position of Arcotheres sinensis. Consequently, we sequenced and annotated the complete mitochondrial genome of A. sinensis , The results revealed that the circular mitogenome of A. sinensis spans 16 520 bp in length. Distinct from typical mitogenomes, A. sinensis contains 13 protein-coding genes (PCGs), 2 ribosomal RNA genes and 23 transfer RNA genes. The A + T content of the A. sinensis mitogenome is 71.63%, with both AT-skew and GC-skew being negative. The lengths of the 23 tRNA genes range from 62 to 72 bp. All tRNA genes exhibit typical cloverleaf structures, except for the trnS1 gene, which lacks the dihydrouridine (DHU) arm. Selection pressure analysis revealed that all PCGs are under evolutionary selection, with cox1 experiencing strongest purifying selection and atp8 undergoing weakest purifying selection. Compared to ancestral Brachyura, the gene order of A. sinensis has been rearranged from R - N - S 1 - E to S 1 - E - N - R and the sequence I - Q - M has transitioned to Q - I - M. Phylogenetic analysis unequivocally positions A. sinensis within the taxonomic framework of the family Pinnotheridae, highlighting its intimate phylogenetic relationship with congeners within the same familial clade, notably Arcotheres purpureus and Pinnotheres excussus. These findings contribute to a better understanding of the status and evolutionary history of Pinnotheridae species. [ABSTRACT FROM AUTHOR]